Typically developing writers in fifth (n = 110, M = 10 years 8 months) or seventh (n = 97, M = 12 years 7 months) grade wrote informative, compare and contrast, and persuasive essays for which the content was held constant--two mountains with a history of volcanic eruption. Relevant background knowledge was provided by reading text and showing colorful illustrations to the students before writing each genre. Results showed considerable variability between genre pairs within and across individual writers in content quality, organization quality, and length. Results, which support multiple expository genres, are consistent with prior research showing multiple genres (narrative vs. expository or even within narrative). Results are discussed in reference to the importance of assessing multiple genres in inferring composing expertise as emphasized by Olinghouse and colleagues.